We’re a day away from the debut of her new film, “Ben Is Back,” at the Toronto International Film Festival, in which she plays Holly, the mother of a 19-year-old opioid-addicted son (Lucas Hedges) who returns from rehab unexpectedly on Christmas Eve.

“It was pretty intense when we were shooting it,” says Roberts, 50, who learned in her research that a parent like Holly struggles with standing firm on just one treatment strategy. “There’s never ‘I’m doing it right.’ Because doing things out of love and hope and belief might be right for an hour, that day or that week, but so quickly the correct thing to be doing could be saying, ‘You’re not welcome in this house.’ "

"Ben Is Back" (in theaters Dec. 7) – a film that could send Roberts back to the Oscars this year, thanks to her tour de force performance – is both timely and gutting: About 2 million people in America are addicted to opioids, according to the Centers for Disease Control and Prevention.

Addiction is no stranger to the Roberts family: Earlier this year Eric Roberts, 62, Julia's elder brother, revealed a decades-long history of drug abuse. But the connection to "Ben Is Back" ends there for Roberts. "The position of the mother in this film is very different from a sister, a niece," she says. "So for me, it was delving into all the mother relationships in these kinds of scenarios that I could find.”

In the film, Ben becomes addicted to prescribed drugs after a snowboarding accident. Roberts, who has twins Hazel and Phinnaeus, 13, and son, Henry, 11, with husband Danny Moder, 49, is watchful of how children are prescribed in her community.

"A lot of my friends who have older teenage kids – older than my teenagers – you get concussions and people get hurt. Kids are playing soccer and things happen," she says, wearing a pair of caramel-framed glasses, her hair pulled into a mussed side braid. "And fortunately the stories that I’ve heard have very much surrounded doctors that say, ‘It’s going to be a bummer, but here’s an aspirin. Suck it up. I’m not going to prescribe anything else for this teenager.' ”

In the Roberts-Moder household, those often-fraught teen years are being confronted as a family unit.

“Fortunately, the five of us are super-close and at dinner, which we have just about every night the five of us are together, it becomes part of the family conversation: ‘Do you know what this is?’ ‘Have you ever heard about this?’ ‘Well, have you ever done that?’ " she says. "It’s about figuring it out together."

That includes vaping, something Roberts calls "a hideous monster in culture now. ... Honestly, I didn’t realize what a thing it was until my oldest son had a swim test at a high school in a neighboring town. I went into the gym to get some water and there was a sign that said: ‘No skateboarding. No loud music. No vaping.’ Like, a permanent sign! And I was like, 'What?' "

"As a parent, I have to put my sort of personal disgust of something aside and be able to have a conversation … as opposed to: ‘Why would anyone do that? It’s disgusting!' "

This weekend Roberts is on double duty in Toronto, where she's also unveiling her first TV series, the upcoming Amazon psychological thriller “Homecoming” (streaming Nov. 2). Based on the popular podcast and directed by “Mr. Robot" creator Sam Esmail, the 10-episode series finds her as a psychologist working with veterans struggling with post-traumatic stress disorder, unaware that darker motivations are at play.

The Oscar winner, who executive-produced the series, acknowledges she's learning as she wades into this era of peak TV.

“The first day I came into the production office I said: 'I don’t understand any of these emails I’m getting. I don’t know what anything means!' ” Roberts laughs. "So I got a quick study in the language of television."

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The just-ended 2018 Toronto International Film Festival offered plenty of star sightings. Click through to see all the celebrities in attendance. Here, Kristen Stewart attends Saturday's premiere of "Jeremiah Terminator LeRoy." Isaiah Trickey/FilmMagic

Amandla Stenberg arrives at a party for "Where Hands Touch," the Holocaust drama in which she stars, playing a biracial teenager who falls in love with the son of a Nazi leader. Charley Gallay/Getty Images for AT&T and DIRECTV